⚡ Bolt: Resolve N+1 latency in admin stats route via concurrent database queries

[secrooq]

💡 What:
Refactored four independent, sequential db.prepare().first() database queries in the src/app/api/admin/[[...slug]]/route.ts /stats endpoint into a single concurrent Promise.all() array, explicitly catching and handling individual errors to maintain fault tolerance.

🎯 Why:
In Serverless SQLite architectures (like Cloudflare D1), discrete sequential SQL queries create severe N+1 latency bottlenecks because each operation requires a separate network roundtrip. Executing them concurrently removes this serialization overhead.

📊 Impact:
Reduces the network latency floor for the Admin Dashboard statistics API by ~75% (from 4 sequential roundtrips to effectively 1 concurrent roundtrip block), resulting in significantly faster dashboard loading times.

🔬 Measurement:

1. Navigate to the admin portal (/admin).
2. Observe faster time-to-interactive for the dashboard statistics cards.
3. Network tab trace of /api/admin/stats will show lower TTFB (Time to First Byte). Tests were fully passing on the branch (pnpm test, npx playwright test).

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PR created automatically by Jules for task 16292621278461871235 started by @secrooq

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